對流不穩定和絶對不穩定攸關磁旋行波放大器是否能穩定操作 的關鍵。Gyro-TWT操作原理根源於前進波的不穩定性，係利用對流不穩定放大輸入訊號；因此，結構造成的反射迴路容易影響輸出訊號的品質。而絕對不穩定所引起的振盪一直是gyro-TWT難以避免的問題，這種利用內部回饋機制形成的不穩定成為阻礙放大效率最主要的原因。為了探討這兩種不穩定對系統造成的影響，本論文針對 模式，第一次諧振模之分佈式損耗磁旋行波放大器進行理論上的分析。在這個系統中，可能存在的振盪來源包括操作在前進波區間的 模式對流不穩定，在電流增大的時候將會激發在cutoff附近的絕對不穩定。另外，還包括第一次諧振模交於返波區間的較低次模振盪，以及第二次諧振模所激發的較高次模振盪。本系統採用分佈式損耗作用段，目的在抑制這些可能產生的不穩定模式。這些由波和電子束同調條件決定的振盪模式涵蓋了一系列從負值到正值的傳播常數，在由損耗段 (lossy section) 和非損耗作用段 (copper section) 組成的線路中呈現了不同的場形包跡。追蹤其中的物理特性，可以解釋不同模式的起振電流對於調變電子和線路參數的敏感度不一。另外配合實際量測結果，我們利用線路結構去模擬反射率對放大波的影響，欲診斷此系統在穩定操作下遇到輸出頻寬不佳的問題。研究發現，出口端的反射是造成飽和輸出功率對頻率響應呈現共振腔特性的原因。這些結果對於目前UC Davis之W-Band磁旋行波放大器實驗上之重要性將在最後討論。

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